Radio access network dynamic functional splits

ABSTRACT

Systems and methods for Radio Access Network dynamic functional splits are de-scribed. In one embodiment, a method may be disclosed for Radio Access Network dynamic functional splits, comprising: determining, by a user for a RAN, a first split of different functionalities between a central Unit (CU) and a Distributed Unit (DU), the functionalities including a Radio Resource Controller (RRC), a Packet Data Convergence Protocol (PDCP), a Radio Link Control (RLC); a Medium Access control (MAC), a Physical Layer (PHY), and a Radio Frequency Unit (RF); and wherein the system is able to provide different splits of the functionalities based on factors such as user count, fronthaul capacity, fronthaul usage, required baseband processing capacity, and latency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Pat. App. No. 62/746,546, filed Oct. 16, 2018, titled “RadioAccess Network Dynamic Functional Splits” which is hereby incorporatedby reference in its entirety for all purposes. This application herebyincorporates by reference, for all purposes, each of the followingpublications in their entirety for all purposes: U.S. Pat. App. Pub.Nos. US20140133456A1, US20150094114A1, US20150098385A1, US20150098387A1,US20160044531A1, US20170013513A1, US20170019375A1, US20170026845A1,US20170048710A1, US20170055186A1, US20170064621A1, US20170070436A1,US20170077979A1, US20170111482A1, US20170127409A1, US20170171828A1,US20170181119A1, US20170202006A1, US20170208560A1, US20170238278A1,US20170257133A1, US20170272330A1, US20170273134A1, US20170288813A1,US20170295510A1, US20170303163A1, US20170347307A1, US20180123950A1, andUS20180152865A1; and U.S. Pat. Nos. 8,867,418; 8,879,416, 9,107,092,9,113,352, 9,232,547, and 9,455,959. The documents incorporated abovefor reference provide detailed information about aspects of an exemplarysystem for implementing the present invention, namely, the documentsdescribe details of the Parallel Wireless HetNet Gateway (HNG) andParallel Wireless Converged Wireless System (CWS) described below.

BACKGROUND

Centralized baseband processing was introduced several years ago to easeinstallation of wireless base stations in large buildings and oncampuses. This was enabled by digital radio interfaces and remote radioheads (RRHs) which allowed the connection between RRHs and digitalbaseband units (BBUs) to be carried over fiber. The concept hassubsequently been generalized to span larger areas involving many radiosites and still using a central BBU. In increasing the deploymentfootprint, fiber and availability of required fronthauls (FHs) became amajor problem.

In recent years, 3GPP and other standards bodies started differentactivities to address this issue. By distributing protocol stacksbetween different components (different splits), solution providersfocus to address the tight requirements for a near perfect FH betweenRRHs and BBUs. However, the approach of the standards bodies has been toprovide multiple potential options, leaving network operators at themercy of equipment vendors' assessment of their likely fronthaul needs.

SUMMARY

Systems and methods for Radio Access Network dynamic functional splitsare described. In one embodiment, a method may be disclosed for RadioAccess Network dynamic functional splits, comprising: determining, by auser for a RAN, a first split of different functionalities between acentral Unit (CU) and a Distributed Unit (DU), the functionalitiesincluding a Radio Resource Controller (RRC), a Packet Data ConvergenceProtocol (PDCP), a Radio Link Control (RLC); a Medium Access control(MAC), a Physical Layer (PHY), and a Radio Frequency Unit (RF); andwherein the system is able to provide different splits of thefunctionalities based on factors such as user count, fronthaul capacity,fronthaul usage, required baseband processing capacity, and latency.

In another example embodiment, a non-transitory computer-readable mediumcontaining instructions for providing Radio Access Network (RAN) dynamicfunctional splits is de-scribed which, when executed, cause the systemto perform steps comprising: determining, by a user for a RAN, a firstsplit of different functionalities between a central Unit (CU) and aDistributed Unit (DU), the functionalities including a Radio ResourceController (RRC), a Packet Data Convergence Protocol (PDCP), a RadioLink Control (RLC); a Medium Access control (MAC), a Physical Layer(PHY), and a Radio Frequency Unit (RF); and wherein the system is ableto provide different splits of the functionalities.

In another example embodiment, a system for providing Radio AccessNetwork (RAN) dynamic functional splits is described. The systemincludes a converged wireless system (CWS); a HetNet Gateway (HNG) incommunication with the CWS; wherein a user is enabled to determine afirst split of different functionalities between a central Unit (CU) anda Distributed Unit (DU), the functionalities including a Radio ResourceController (RRC), a Packet Data Convergence Protocol (PDCP), a RadioLink Control (RLC); a Medium Access control (MAC), a Physical Layer(PHY), and a Radio Frequency Unit (RF); and wherein the system is ableto provide different splits of the functionalities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing example deployment cases, in accordance withsome embodiments.

FIG. 2 is a diagram showing a system having an HNG and multiple CWSs, inaccordance with some embodiments.

FIGS. 3A and 3B are a diagram showing a 4G solution based on split 1, inaccordance with some embodiments.

FIGS. 4A and 4B are a diagram showing a 4G solution based on split 6, inaccordance with some embodiments.

FIGS. 5A and 5B are a diagram showing a 4G solution based on split 2, inaccordance with some embodiments.

FIGS. 6A and 6B are is a diagram showing a 4G solution based on split 6,in accordance with some embodiments.

FIGS. 7A and 7B are a diagram showing a solution based on split 7.1 inaccordance with some embodiments.

FIGS. 8A and 8B are a diagrams showing a solution based on split 8 inaccordance with some embodiments.

FIGS. 9A and 9B are is a diagram showing a 4G solution based on split 8in accordance with some embodiments.

FIG. 10 is a diagram showing Fs-C and Fs-U interfaces toward a RAN, inaccordance with some embodiments.

FIG. 11 is a diagram showing a VRU to HNG as an aggregator in accordancewith some embodiments.

FIGS. 12A and 12B are a diagram showing a solution based on split 6 inaccordance with some embodiments.

FIGS. 13A and 13B are a diagram showing a solution based on split 1 inaccordance with some embodiments.

FIGS. 14A and 14B are a diagram showing a solution based on split 1 inaccordance with some embodiments.

FIGS. 15A and 15B are a diagram showing a solution based on split 6 inaccordance with some embodiments.

FIGS. 16A and 16B are a diagram showing a solution based on split 7.1 inaccordance with some embodiments.

FIGS. 17A and 17B are a diagram showing a solution based on split 6 inaccordance with some embodiments.

FIGS. 18A and 18B are is a diagram showing a solution based on split 2in accordance with some embodiments.

FIG. 19 is a diagram showing a wherein a new RAN is coupled to multipleNGC in accordance with some embodiments.

FIG. 20 is a diagram showing a 5G migration options in accordance withsome embodiments.

DETAILED DESCRIPTION

Parallel Wireless's dynamic architecture is the only available solutionfor mobile operators to utilize different splits based on morphology andinfrastructure availability. While for rural deployment higher splitsare more desirable, for dense urban areas lower splits will be theoptimum solution. Parallel Wireless's dynamic solution will enablemobile operators to pick and choose different splits based on the samehardware and network components by using different softwareimplementations. Different protocol layers will reside in differentcomponents based on FH availability and morphology. This approach willdramatically reduce the cost of operations and ownership for mobileoperators.

The logical topology of FH will be diversified in the future 5Gnetworks. As mentioned previously, centralized cooperative processingrequires an FH network to aggregate (distribute) information from (to)multiple RRHs to a BBU or transport information between BBUs. This willnot be an optimal solution to be applied for different deploymentscenarios based on different morphologies. Therefore, as a part of 3GPPframework, multiple functional splitting has been proposed to meet thesediverse requirements. It is clear that the existing C-RAN concept (split8) is an optimal solution for future systems. We believe a dynamicfunctional split between a central unit (CU) and distributed unit (DU)will be the approach for 5G systems and beyond. While CUs will maintainBBU-like functionalities, DUs will be more than RRH in terms ofprocessing capacities. In case of requirements for more delay-sensitiveservice in 5G (including but not limited to beamforming andconfiguration), based on appropriate FH availability, the MAC-PHY splitwill be the preferred solution. Parallel Wireless believes the future 5Gis not about specific split but more about flexibility and the abilityto create different splits based on different morphologies anddeployment scenarios. Parallel Wireless 5G RAN visualization willaddress all these requirements through its HetNet Gateway (HNG) as ananchoring point and aggregator.

For migration to 5G there may also be the need to transport informationamong DUs when cooperative processing functions are placed at DUs.Moreover, when the function splitting scheme is dynamically changed, theFH networking topology needs to be adapted accordingly. At ParallelWireless we have already utilized dynamic functional splitting byutilizing our HNG and Converged Wireless Systems (CWS) for 3G and 4Gdeployments.

RAN virtualization brings the flexibility to decouple the radio and RFfrom the base band processing and allocate resources, when and whereneeded, in the most optimized manner. The Parallel Wireless solutionprovides all necessary functionality to address this requirement basedon its HNG by providing abstraction, core network isolation and resourceutilization. This is optimal for rural and remote areas with lowernumbers of users, lower traffic and less than perfect FH. The ParallelWireless 3G/4G solution is deployed across the world with HNG as theaggregator located remotely in operators' colocation facilities and CWSsact as a compact RRH/BBU single unit with different FHs includingcommercial LTE services and DSLs.

In super dense areas; e.g. stadium, shopping malls, the general tendencyis moving toward legacy split 8. While BBUs are going to be located inthe vicinity, a low latency and reliable FH (CPRI type of connection)can connect all RRUs to the central local location. While ParallelWireless can support such a scenario, HNG capabilities can eliminate theneed of super low latency and reliable FH links to a more available andcheaper solution like standard cat5/6 connections and reduce the cost ofimplementation dramatically. The present document intends to approachthe evolution of RAN towards virtualization together with the impacts onthe underlying transport network, in segments like fronthaul, midhaul orbackhaul, depending on the functional split considered on the radiopart. The potential deployment cases into consideration are reflected inFIG. 1.

Parallel Wireless 3G/4G solution is based on HetNet Gateway (HNG) as thegateway between operator's core networks (Aggregator) and ConvergedWireless System (CWS)s. Parallel Wireless's innovative solution alreadydeveloped based on Split 0 general access schema in mind to provide aneasy migration path toward 5G while reducing the impact of less thanperfect fronthaul in system performance. From core network perspectiveHNG will act as a single (e)NodeB (E)UTRAN and act as the aggregator.CWSs are compact (e)NodeBs including RRU/DU/CU. In all deployedscenarios, a less than perfect fronthaul between HNG and CWS providesconnectivity while maintaining required QoS. This is shown in FIG. 2.

HNG

Parallel Wireless HetNet Gateway (HNG) logically sits between RadioAccess Network (RAN) and core network, and abstracts RAN on any COTShardware for core network. At the same time, making RANself-configuring, self-optimizing, and self-healing through itsSelf-Organizing Network (SON). The Parallel Wireless solution utilizesstandard backhaul and provides more robustness by its splitfunctionality. By virtue of having detailed information about all thebase stations on the network, as well as all the UEs on the network, theHNG is positioned to determine, based on a large number of potentialfactors, what the appropriate functional split is for a given networkcontext, and can control the CWS (base station) to utilize theappropriate split.

CWS

Parallel Wireless Converged Wireless System (CWS) is a cost-effectiveand compact eNB. They are software-defined multi-mode multi-carrier basestations coming in different transmit powers. They can utilize any typeof preferred external antenna via a 4.3-10 low PIM connector. Thecompact all-in-one design approach helps to achieve the right level ofsystem capabilities and attractive economics for fixed wireless serviceproviders to deliver a wide-variety of deployments with the extremelylow cost per unit coverage ratio. The CWS operates in conjunction withthe HNG (for management) and with the VRU (for baseband processing).

VRU

Based on any COTS hardware, this component provides MAC, RLC and PDCPfunctionality to one or more CWSes, e.g., in a centralized fashion. Itcommunicates to a cluster of CWSs (RRH/DU) and supports multiplecarriers based on the CWSs' load. The interface between VRU and CWSs canbe based on Ethernet based eCPRI, in some embodiments.

Parallel Wireless has already developed its innovative 3G/4G solutionbased on Split 0 access schema, and its solution is open for any otheraccess schema and split modification based on specific requirements. Forexample, in case of requirements for more delay sensitive service in 5G(including but not limited to beamforming and configuration), ParallelWireless virtual radio unit (VRU) can still act as the aggregator andsplits 1, 2 or 3 utilize based on appropriate fronthaul availability andpreferred split option (in this specific case, MAC-PHY split). ParallelWireless believe the future 5G is not about specific split but moreabout flexibility and ability to create different splits based ondifferent morphologies and deployment scenarios. Parallel Wireless 5GRAN visualization will address all these requirements through thecombination of its HNG and VRU as anchoring point and aggregator.

RAN virtualization brings the flexibility to decouple the radio and RFfrom the base band processing and allocate resources; when and whereneeded, through the most optimized manner. Parallel Wireless solutionprovides all necessary requirements to address this requirement based onits HNG and VRU by providing abstraction, core network isolation andresource utilization.

Specific functional splits are described hereinbelow.

Split 0

For 3G deployments, HNG concentrates all NodeBs and provide singleconnectivity to Packet Switched (PS) and Circuit Switched (CS) corenetworks through standard Iu-cs and Iu-ps. As it mentioned before, fromcore networks perspective, there is one NodeB deployed in the network.Also, HNG will act as a Virtual RNC (vRNC) and aggregates all CWSs as asingle NodeB. Using HNG as an aggregation point toward core network,will reduce network related delays for services like Circuit SwitchedFall Back (CSFB) while users are connected to LTE network and needs togo back to 3G or 2G network for voice (circuit switched) services.

For LTE deployments, HNG concentrates all eNodeBs and provide a singleS1-U connection to S-GW for data traffic and a single S1-MME connectionto MME for all signaling and control related traffic. In this case, HNGwill act as an aggregator of S1 signaling toward S-GW and MME. This willreduce all handover and paging related signaling and control messagestoward core network (EPC).

This option would be an ideal solution for deployments with lowthroughput and high latency (e.g., satellite). While HNG acts only asaggregator and anchoring point toward the core for reducing signalingand all SON functionalities, all other functionalities are embedded inthe CWS. These include RF, PHY, MAC, PDCP and RRC. This architectureworks with low throughput and very high latency backhauls and could bethe best solution for remote rural deployment without sufficientinfrastructure. In case of high traffic load, there may be need foradding VRU.

In general, for rural and remote areas with lower number of users, lowertraffic and less than perfect fronthauls, access schema split 0 is thepreferred one. At the moment, Parallel Wireless 3G/4G solution deployedacross the world with VRU as the aggregator located remotely inoperator's colocation facilities and CWSs act as a compact RRU/DU/CUsingle unit with different fronthauls including commercial LTE servicesand DSLs.

On the other extreme in super dense areas; e.g. stadium, shopping malls,the general tendency is moving toward access schema split 4. WhileDU/CU/Aggregator are going to located in the vicinity, a low latency andreliable fronthaul (CPRI type of connections) can connect all RRUs tothe central local location through segment 4A. VRU capabilities caneliminate the need of super low latency and reliable fronthaul links tomore available and cheaper solution like standard cat5/6 connections andreduce the cost of implementation dramatically.

Parallel Wireless has successfully deployed its 4G solution based onsplit 1 and utilizing access schema split 0 across the world as it isshown in the following figure. HNG acts as an aggregator and includesSON functionalities. The fronthaul can be standard commercial LTEnetwork (through the Internet) or other legacy WANs. This approachdramatically reduces the cost of deployment and OPEX by utilizingcommercially available access networks as its fronthaul for many ruraland semi urban morphologies. This is shown in FIGS. 3A and 3B, and alsoin FIGS. 4A and 4B.

For deployment in dense urban areas, Parallel Wireless has successfullyutilized split 7, in order to keep RF and PHY at CWSs and using lessthan perfect fronthauls to connect them to HNG which hosts PDCP, RLC,and MAC as the centralized unit. Parallel Wireless's flexiblearchitecture makes deployment of 4G solution easy and seamless sincebase on morphology and availability of fronthaul its technology canadapt to available resources.

Split 2

Split 2 is recommended for deployment in rural and semi-urban areas withnon-ideal backhaul. In the Parallel Wireless Solution split 2 could berealized with RRC, S1-U (data) and PDCP functions to be hosted in VRU inclose proximity to the CWS and the Lower layers RLC, MAC and PHY on theCWS. This option allows some part of the stack to be virtualized at theVRU and connected to the aggregator (HNG) through a less than perfectbackhaul. The PDCP RLC split is already standardized in the LTE dualconnectivity. This is shown in FIGS. 5A and 5B

This option would be ideal in case the FH options are not able to ensurethe latency/jitter requirements of some of the lower split options andin implementation would mean a very straight and clean split. Theoverhead of traffic is also minimal and is comparative to non-split FHrequirements. Option 2 split enables virtualization of some part of thestack function and also provides the option to reduce processingoverheads on the RRH or DU. Another advantage of this split option,especially with the Parallel Wireless solution, is the Dual Connectivitywill be very efficiently implemented and back routing of data packetsover the X2 interface is avoided. Since the VRU is close to the CWSs andcan support many of them in a close proximity, there is significantoverhead reduction in packet routing when the Option 2 split isimplemented.

Based on 3GPP TS 36.213 for DL, 8 layers, 256QAM, the TB bits are 391656(per TTI), therefore the maximum downlink throughput will be 391 Mbps.For uplink, assuming category 17/19 (supporting 256QAM) the UL TB bitsare 211936 (per TTI) therefore the maximum UL through put will be 212Mbps.

Considering the 5% overhead, the maximum bi-directional link capacityfor split 2 will be:(391+212)*1.05=637 Mbps

Also, latency up to 25 msec will be tolerable for this split.

Split 2 can be a great candidate for rural and deployments with lessthan perfect transport availability. For remote locations withsatellite, DSL or commercial LTE as the only option for FH this splitwill be the perfect solution. However, because the DU needs to hostPHY/MAC/RLC close to RRH, the remote units are more complex andexpensive.

Split 6

For deployment in dense urban areas, Parallel Wireless has successfullyutilized split 6. In this architecture, the CWS contains RRH and the DUincludes RF and PHY. VRU will be in close proximity to CWS and hostPDCP, RLC, and MAC as the CU. In this architecture a CU can supportmultiple CWSs collocated on the same tower or rooftop. While the FH canbe a 1G/10G type of connection, the backhaul to HNG can be a less thanperfect connection. Parallel Wireless's flexible architecture makesdeployment of the 4G solution easy and seamless since base on morphologyand availability of backhaul, its technology can adapt to necessaryresources. This is shown in FIGS. 6A and 6B.

Legacy centralized baseband (split 8) in most cases promises loadbalancing between sites, taking advantage of the fact that peak loads donot occur uniformly. However this must be balanced against any increasein the cost required to achieve the load balancing, e.g., for switchingradio traffic between different processors. Field studies have foundthat a relatively small number of base stations still provide goodheterogeneity, and that most of the potential for load balancing gainscan be leveraged with about 20 sites. In addition, certain“computationally expensive” processing tasks such as fast Fouriertransform/inverse fast Fourier transform (FFT/IFFT) are not loaddependent and exhibit no sharing gains. Also, considering HARQmanagement at the MAC level is one of the most traffic related processesit will be beneficiary to utilize split 6 for scenarios where there aresites with different demographics (e.g., business and residential) andless than perfect backhauls in terms of latency (around 8 msec RTT).

Transport Requirements

Based on 3GPP TS 36.213 for DL, 8 layers, 256QAM, the TB bits are 391656(per TTI) therefore the maximum DL throughput will be 391 Mbp. Foruplink, assuming category 17/19 (supporting 256QAM) the UL TB bits are211936 (per TTI) therefore the maximum UL throughput will be 212 Mbps.

Considering the 30% overhead, the maximum bi-directional link capacityfor split 6 will be:(391+212)*1.3=784 Mbps

Considering the 8 msec RTT requirements (discussed in AR33), standard 1GWAN connections would be sufficient for split 6 FH.

For calculating the required RTT for this split, we must look into HARQtiming for PRACH and regular data transmission. For the PRACH, eNB isrequired to answer to the UE within a configurable random-accessresponse window. This window starts three subframes after the lastsubframe with the respective preamble transmission and has aconfigurable length between two to ten subframes. Considering theshortest duration for two subframes (2 msec), the UE must receive itsresponse before 4 msec. Considering maximum ranges for LTE (100 Km) andits related timing advance (0.67 msec) and about 1.5 msec for processingtime at the CU, it left us with 2 msec RTT for latency between MAC andPHY. Therefore, a maximum one-way latency of 1 msec is required for thissplit. The standard synchronous transmission and ACK messages which have8 msec (8 subframe after the initial one) delay budget will not be adominant factor for this requirement.

Split 6 is well-balanced for urban and dense urban deployments. Whilethe CU can accommodate lots of computationally expensive and loadrelated functionalities of MAC/RLC/PDCP, RU just host the complete PHYstack. The FH requirements are also reasonable and not as tight assplits 7 and 8. However, there is still a need for limited processingpower as part of DU close to RRH.

Split 7.1

Parallel Wireless recommends option 7.1 split of 3GPP for the case whenhigh throughput and low latency FH is available between VRU and the CWS.This is a very efficient and practical PHY split, considering IFFT/FFTare not load dependent and add no sharing gain by accommodating it inthe CU. All other PHY functionalities including coding, modulation,layer mapping and precoding will be located at the CU while IFFT/FFT andCP addition/removal and Radio will be collocated at the DU. Our CWS, VRUand HNG products are naturally equipped to support Split 7.1 asdiscussed before. Our CWS is composed of an integrated radio front endthat serves as a DU which is responsible for antenna to basebanddown-conversion (and baseband to antenna up-conversion) and IFFT/FFT andCP addition/removal. VRU will host all other parts of the stack as theCU, while HNG acts as the aggregator. This is shown in FIGS. 7A and 7B.

Considering IFFT/FFT and CP addition/removal, the only parts of overallprotocol stack which are not load dependent and they are in DU for split7.1, this split can be utilized for extreme load balancing scenarios.For morphologies and geographical areas with very non-uniform peakloads, this split can exhibit maximum sharing gain.

Transport Requirements

The requirements for FH capacity can be calculated as the following:

DL

For a 20 MHz channel, 256QAM and 8 layers the required bitrate is:

100 (PRB)×12 (no of subcarriers per PRB)×14 (symbols)×8 (bits persymbol)×8 (layers)×2 (I/Q)/1×10−3

(one subframe)=2.15 Gbps

UL

For a 20 MHz channel, 64QAM and 8 layers the required bitrate is:

100 (PRB)×12 (no of subcarriers per PRB)×14 (symbols)×6 (bits persymbol)×8 (layers)×2 (I/Q)/1×10−3

(one subframe)=1.61 Gbps

For split 7.1 the FH needs to support 3.76 Gbps bidirectional

The one-way latency of 250 microseconds is expected for split 7.1option.

Split 7.1 is a good solution for dense urban areas. Consideringcolocation of lower PHY with RRH, IFFT/FFT functionalities that are notload related will be handled remotely. However, close to perfect FH withlatencies below 250 microseconds is required.

Split 8 (C-RAN)

Since RAN deployment and operations takes approximately up to 80% ofCAPEX and 60% of OPEX, it has been identified as the main candidate forcost saving in the future deployments. The cloud-based radio accessnetwork (C-RAN) was the first attempt in this direction. It evolved fromthe traditional base stations (BSs) where processing units and radios(RFs) were integrated. The processing capacity of these BSs are used forproviding services to mobile users (UEs) attached to them and could notshare in a large geographical area. The main drawback for legacy BSs wasunderutilization of available processing power in each BS. While BSs inbusiness areas are overloaded during the day, the ones in residentialareas are almost idle. Due to the increase in in data traffic demands inthe recent years, the differences in peak usage in differentmorphologies causes a huge amount of idle processing powers for certainBSs during the day.

To overcome this challenge, the C-RAN concept was introduced anddeployed in recent years. C-RAN is based on centralized processing tocombine all BSs' computation and processing resources into a centralpool called baseband unit (BBU). The BBUs are a set of physical serversin a data center which enables communications among BSs with lowlatencies. The BBUs are connected to remote radio heads (RRHs); whichtransmit and receive signals, through fronthauls (FHs). All protocolstacks are located at BBU and only RF functionality remains at RRU.Since all protocol stacks including physical (PHY) layer are located atBBU, the FHs need to have low latency and high throughputs compared tolegacy backhauls to BSs. Also, they need to provide tightsynchronization and allow point to point logical topology. Common publicradio interface (CPRI) based fiber connections are the standard solutionfor FHs. This can be seen in FIGS. 8A and 8B.

Parallel Wireless recommends option 8 split of 3GPP for the case whereperfect FH is available between VRU and the CWS. Since all DU and CUfunctionalities are located at VRU, CWS will act as an RF transmittedreceiver and all base band processing will be conducted at VRU. Sincethe FH needs to carry all IQ data, it must be a CPRI based interface tomeet the requirements. This is shown in FIGS. 9A and 9B.

Transport Requirements

Based on 3GPP R3-162102, considering a 20 MHz channel size, with IQbandwidth of 2*16 bits and 32 antenna digital ports for both uplink anddownlink the required FH through put is:30.72*32*32 Mbps=31.4 Gbps

With a latency of less than 250 micro second.

Advantages and Disadvantages

Pros: More energy efficient and simplifies the inter-BS coordination,they have their own limitations.

Cons: Although this split minimizes the functionality at RRH,requirements for CPRI FH make it necessary to accommodate DU in theclose proximity to RRH, thereby limiting deployment options. Also, someof the computationally intense processing tasks such as fast Fouriertransform/inverse fast Fourier transform (FFT/IFFT) are not loaddependent and exhibit no sharing gains, therefore there is no gain tocentralize lower PHY.

Other major issues include:

Massive FH bandwidth requirements: The bandwidth requirements of aclassical FH link are proportional to the product of radio bandwidth,number of antennas, and quantization resolution. To put this intoperspective, a typical 20 MHz 4G LTE eNodeB with 8 antennas requiresaround 10 Gb/s FH bandwidth on uplink (UL) or downlink (DL). Since thearea density of antennas and the communications bandwidth are bothexpected to be even higher in 5G networks, the demand for FH bandwidthwill become even more significant. The most straightforward option forphysical transport is dark fiber, in which one fiber core can only carryone FH link. However, this will result in enormous fiber resourceconsumption, making this scheme realistic only to operators withabundant fiber resources or in scenarios where fiber deployment ischeap. Another option is to multiplex FH links into a single fiber coreusing wavelength-division multiplexing (WDM), but WDM modules are stillmuch more expensive than black and white modules.

Stringent latency constraints: Wireless signal processing often hasstringent latency constraints. For example, the LTE hybrid automaticrepeat request (HARD) process leaves a latency budget of 3 msec for thedecoding of each radio subframe. Because subframes need to first betransported from RRHs to BBUs before being processed, the transportationlatency should also be counted into this latency budget. Excluding theportion necessary for signal processing (about 2.5 msec), there are only300 to 500 msec left for FH transportation, ruling out anyswitching-based technologies that will incur excessive latency [2].Moreover, some future 5G communication scenarios demand even stricterlatency constraints: for sub-millisecond wireless access, the latencybudget for FH transportation will be so small that any long-rangetransportation may be prohibited.

Tight synchronization requirements: Many RRHs cannot generate anaccurate clock by themselves, either because GPS receivers are tooexpensive to be integrated into RRH or due to satellite signal blockagein indoor environments. For this reason, FH must deliver synchronizationinformation from BBUs to RRHs. In CPRI links, clock information iscarried in the waveform (pulse edges) of the transported signal. But theunderlying network infrastructure may introduce jitter to the waveform,leaving degraded communication performance. The importance of tightsynchronization will be even greater in 5G networks because of themassive cooperation between access nodes. If cooperating access nodeshave frequency offset, their transmitted signals will overlap at UE, andwill not be able to be separated and individually compensated, causingdistorted beamforming patterns and degraded performance.

All functionalities except RRU (PHY/MAC/RLC/PDCP) are located in acentral facility and a high bitrate/low latency front haul connect CWSsto HNG. Although Parallel Wireless solution will support this case, itis not the preferred solution due to cost and CPRI like fronthaulrequirements.

Parallel Wireless's CWS, VRU, and HNG products are naturally equipped tosupport Split 8. Our CWS is composed of an integrated radio front endthat serves as a DU which is responsible for antenna to basebanddown-conversion (and baseband to antenna up-conversion). Our CU iscomprised of highly scalable general-purpose processors and FPGAs thatcontain the LTE protocol stack along with the LTE baseband processing tosupport multiple high-capacity LTE carriers (i.e., 3 to 6 sectors, 20MHz, 4×4). The interface between the DU and the CU is a standard CPRI.

With Split 8 we can seamlessly support many high-end LTE features suchas CoMP, massive MIMO, and load balancing in a highly mobile radioenvironment. Our split 8 option allows for centralized trafficaggregation from NR and E-UTRA which in turn enables us to smoothlymigrate from the LTE ecosystem to the NR ecosystem. Since virtually allof the LTE protocol stack runs on the CU over GPP/FPGAs, by leveragingstatistical multiplexing of compute resources we could enable energyefficient radio resource management. As the DU and CU are split at theRF component levels, changes in the PHY and protocol stack are bettermanaged and RF components can be shared across the RAN technologies andalso be easily upgraded.

For Split 8, due to the RF and protocol stack separation, the transportrequirements go linearly with the number of supported antenna ports.With 8 antenna ports per 20 MHz carrier, the transport requirements are9.8304 Gbps per direction (CPRI Rate-7) whereas with 12 antenna portsthis rate increases to 12.1651 Gbps (CPRI Rate-9). We believe our nextgeneration DU and CU with PCIe (3.x, 16 lanes) comfortably support thesetransport requirements.

The one-way latency with Split 8 is expected to be around 250 micro sec.

As our Split 8 is based on the industry-standard CPRI, our CU and DU areinteroperable with third party CU/DUs.

The main advantages of split 8 are that the baseband resources arecentrally pooled and the RF and PHY are decoupled. These allow us toscale the network to accommodate many sectors, multiple channelbandwidths and pave the way for massive MIMO operation. Interferencemitigation, coverage expansion, joint transmission and reception,supporting a large UE count in both UL and DL, and energy-efficientradio resource management are some of the biggest advantages of split 8.Software-centric and commodity HW further make this split veryattractive from the cost reduction standpoint.

The central drawback of split 8 is that the fronthaul (the link betweenCU and the DU) data rate and latency requirements grow with the numberof antenna ports. The fronthaul latency is expected to be within 250microsec as recommended by the 3GPP 38.801 technical report whereas thefronthaul rate could be as high as 160 Gbps with 100 MHz channelbandwidth and 32 antennas.

Our split 8 DU consists of a radio front end with optional PA (poweramplifier) pre-conditioning functionality (DPD and CFR; DPD: digitalpre-distortion and CFR: crest factor reduction). The DPD and CFR can beimplemented on an industry-standard FPGA. As a result, GPP processing isminimal (to around 10-20%) in the DU. On the other hand, our CU consistsof the entire LTE protocol stack (which includes the Layer 1 PHYtogether with the MAC/Scheduler/RRM etc). The layer 1 PHY is implementedin both GPP (channel estimation, equalization, layer mapping, MIMOprecoding etc) and FPGAs (decoder acceleration).

Our CU portion of the split 8 solution leverages both GPP and FPGAs. Weemploy RTOS to orchestrate the HW resources running on the FPGA forLayer 1 PHY processing. The same RTOS is also powering our scheduler,MAC, RLC, PDCP, RRC and RRM functionality in the higher layers of theprotocol stack. Our GPPs can be commodity server chips based on x86architecture and the SW can run on a version of real-time Linux.

Path to 5G

Parallel Wireless believes its existing 4G solution is well positionedto create a seamless evolution path toward 5G. While new 5G radios caneasily added to CWS, our VRU and HNG can act as aggregator and can alsoprovide different functionality based on appropriate splits. Also,Parallel Wireless HNG can act as an aggregation point toward 5G corenetwork and manages all network slicing based on Network Slice SelectionAssistance information (NSSAI) and manage all related gNB and reducingcore network signalling dramatically. This approach can providecontinuity for mobile operators 5G role out by utilizing a singleaggregator as anchoring point toward their 4G and 5G by utilizing asingle HNG. This will provide the path to gradually retire CU physicalequipment and create a simpler architecture purely based on CWS and HNG.

Because of utilizing HNG, Parallel Wireless solution can utilize anysplit type based on different deployment scenarios. It provides acomplete separation between Control Plane (CP) and User Plane (UP) andmakes it possible for UEs to connect to multiple transmission pointssimultaneously. HNG will centralize all CP related functions toward 5GRAN; and 4G RAN, controlling different transmission nodes and achievesenhanced radio performance. Parallel Wireless will comply with future3GPP standards by utilizing Fs-C and Fs-U interfaces toward RANtherefore gNBs from different vendors can also be connected to HNG andmanaged by it. This will reduce overall control and signalling traffictoward the core network and improve overall radio network performance.This is shown in FIG. 10.

The future evolution of RAN will be toward dynamic functional splits.While an aggregator acts as a mediator between RAN and core network, thefunctionality of the RAN will be distributed between DUs and CUs. Indifferent scenarios, these elements can collapse together and create asingle physical entity with different virtual functionalities.

The centralized baseband deployment is initially proposed to allowload-balancing between different base stations. Therefore, in most casesDU will be collocated with RRH to conduct all computationally intenseprocessing tasks such as fast Fourier transform/inverse fast Fouriertransform (FFT/IFFT) which are not load dependent and exhibit no sharinggains. CU can be separate or collocated with the aggregator depending onFH availability.

Same as Parallel Wireless 4G solution, our 5G solution will support adynamic split approach based on deployment scenarios. For the ruraldeployment, with lower number of users, low traffic and less thanperfect fronthauls, option 1 split between HNG (RRC) and CWS(PDCP/RLC/MAC/PHY/RF) is the most desirable solution. Whereas in denseurban areas option 6 split between HNG (RRC/RLC/MAC) and CWS (PHY/RF)can be a better solution.

The Parallel Wireless CWS already provides RRH and DU functionality inone unit. It will be easy to deploy any of the discussed splits due tothis availability. We believe split 6 will be the best approach goingforward for deploying future mobile network in different environmentsand morphologies. While its requirements for fronthaul is not asrestricted as split 8, by utilizing Virtual Radio Unit (VRU)¹ oursolution can support traffic in a dense urban area while maintaining aless than perfect backhaul to connect this local VRU to the HNG asaggregator. In some figures or portions of this disclosure the VRU maybe referred to as a VBBU (virtual baseband unit). This is shown in FIG.11.

Also, for rural areas where there is no reliable and high capacityfronthaul availability, the local VRU connection to CWS will utilize aclose to perfect fronthaul since they are in close proximity and utilizeless than perfect backhauls (e.g. satellite links) to connect the VRU tothe HNG. All these scenarios will be discussed in detail in thefollowing sections.

Parallel Wireless's innovative and flexible approach makes thedistribution of functions and different splits easy to implement. Themain components will be our HNG and CWS, however the functionalitydistribution between CU and DU can be configured based on requirements.The CU can be located at colocation facilities, while DU will be ourCWS. Split 6 in this case will be the most suitable option, howeverParallel Wireless solution can utilize all other defined splits as well.By this split, latency requirements for FH are not as restricted assplits 8 or 7.

Although Parallel Wireless supports option 7.1 split of 3GPP, we believefor dense urban scenarios when near perfect FHs are available, split 6provides a better diversity gain. Pushing IFFT/FFT to DU will relaxrequirement for FH, but still it requires a near perfect FH which can bechallenging in many deployments. This is shown in FIGS. 12A and 12B.

Parallel Wireless has understood that it is a significant advancement tobe able to dynamically change the functional split and distributefunctionalities/network elements based on capacity/latency of fronthaul.A new network element, VRU (Virtual Radio Unit), is introduced that cancontinuously evaluate the fronthaul capacity/latency, via communicationwith base stations, and dynamically allocate, enable and utilizeprotocol stacks on CU and RU to match the available fronthaul capabilityat any time. In some figures or portions of this disclosure the VRU maybe referred to as a VBBU (virtual baseband unit). This is enabled by ourmodular architecture, and by the fact that our GPP/FPGA HW at our CWScan provide enough horsepower to run protocol stacks at the edge as wellas at a centralized node. Additionally, the VRU can provide auxiliarybaseband processing capability to supplement, augment, and load-balancea plurality of managed CWS nodes. Multiple VRUs may be used in thenetwork. The VRU may be located in the network physically close to theRAN and in a network-proximate location to the RAN, and may operate inconjunction with the HNG, which may be located at the core network edge.The HNG may coordinate multiple VRUs as well as multiple CWSes.

Further, using the SON manager at the HNG, which enablesself-configuration, a dynamic software-based radio can be enabled thatcan that configure each network element protocol stack (our CWSdirectly, or via VRU) based on the current morphology. Specifically, notonly are changes in configuration contemplated, like legacy SONs, butrather, we configure each network elements protocol stacks as required.

Our solution includes a modular software base, that give us theopportunity to dynamically allocate the modules (layers) that we need toeach HW component (CWS or VRU). We consider PHY, MAC, RLC and PDCP asfour different software modules. Our CWS GPP and our VRU hardware canprocess each module based on how we split them and load them. In split 6for example, we let CWS run PHY while other 3 modules (layers) will berun on VRU hardware. We can dynamically change these splits based onmorphology and availability of fronthauls at the time of deployment, orchange them later on. Likewise, for split 2, we keep PDCP at the HNG andpush all other layers to the CWS. We believe the concept of pure RRU(just dumb radio at the edge) is not scalable due to high throughput (+2Gbps) and very low latency (less than 250 micro sec) fronthaulrequirement. We can interoperate with our own or third party hardware,either radio for CWS part or COTS server for VRU, and the coordinatingnode can sit in the middle and decide how much to load to each radio andrun the rest at the gateway (HNG).

Further details regarding specific functional splits is below.

Parallel Wireless has already deployed 4G networks across the globebased on option 1 split between HNG (RRC) and CWS (PDCP/RLC/MAC/PHY/RF).Also, option 6 split between HNG or VRU (RRC/RLC/MAC) and CWS (PHY/RF)is an available alternative. In this case, PHY layer and RF will residein CWS (acting as the 3GPP distributed unit, or DU) and all otherfunctionalities remain in VRU (acting as the centralized unit, or CU,and Aggregator). The interface between CWS (DU) and VRU (CU/Aggregator)will carry data, configuration and scheduling related informationincluding MCS and resource block allocations. This option makes jointtransmission and inter layer coordination feasible. However, asmentioned previously, Parallel Wireless system can utilize other splitoptions if it is required.

Because of our HNG anchoring capabilities, the same approach (like 4G)is applicable. Parallel Wireless has already deployed 4G networks acrossthe globe based on option 1 split between HNG (RRC) and CWS(PDCP/RLC/MAC/PHY/RF). Also, option 6 split between HNG/VRU(RRC/RLC/MAC) and CWS (PHY/RF) is an available alternative. In thiscase, PHY layer and RF will reside in CWS (DU) and all otherfunctionalities remain in VRU (CU/Aggregator). The interface between CWS(DU) and VRU (CU/Aggregator) will carry data, configuration andscheduling related information including MCS and resource blockallocations. This option makes joint transmission and inter layercoordination feasible. However, as it mentioned before, ParallelWireless system can utilize other split options if it is required.

This is Parallel Wireless's 4G innovative approach. Parallel Wirelesshas successfully deployed its 4G solution based on split 1 and utilizingaccess schema split 0 across the world. Parallel Wireless has alreadydeployed 4G networks across the globe based on option 1 split betweenVRU (RRC) and CWS (PDCP/RLC/MAC/PHY/RF).

Same approach is applicable for 5G and Parallel Wireless utilize itbased on following figure. This is shown in FIGS. 13A and 13B.

Parallel Wireless's innovative and flexible approach makes thedistribution of functions and different splits easy to implement. Themain components will be our VRU and CWS, however the functionalitydistribution between Aggregator, CU and DU can be configured based onrequirements. For case one, the aggregation of Aggregator and CU cancombine and perform at colocation facilities, e.g., at a VRU, whileRRU/DU will combined in our CWS. Split 6 in this case will be the mostsuitable option, however Parallel Wireless solution can utilize allother defined splits as well. While Aggregator and CU can utilize samehardware or different hardware, they will be collocated. By this split,latency requirements for Segment 1A are not as restricted as splits 8 or7. This is shown in FIGS. 14A and 14B and also in FIGS. 15A and 15B

Parallel Wireless believes Case 2 will not bring much value whencompared to Cases 1 and 3. Separation of RRU and DU requires low latencyand high throughput for Segment 2A, while separation of PHY (includingIFFT/FFT) from RRU to make it centralized for multiple RRUs does nothave any benefit. Most of the PHY functionalities (specificallyIFFT/FFT) are not load related, therefore there will be no loadbalancing gain.

Parallel Wireless envision this scenario for the scenarios wheremultiple CWSs deployed in areas and a single VRU (hosting DU/CU) withclose physical proximity to them will deployed to control them. This canbe the case when fronthaul availability is limited to short distancesand VRU needs to be close to CWSs. In this case a split 6/7 is feasibleat the remote VRU.

Parallel Wireless supports option 7.1 split of 3GPP. This is a veryefficient and practical PHY split, considering IFFT/FFT are not loaddependent and add no sharing gain by accommodating it in the CU. Allother PHY functionalities including coding, modulation, layer mappingand precoding will be located at the CU while IFFT/FFT and CPaddition/removal and Radio will be collocated at the DU. Our CWS and VRUproducts are naturally equipped to support Split 7.1 as discussedbefore. Our CWS is composed of an integrated radio front end that servesas a DU which is responsible for antenna to baseband down-conversion(and baseband to antenna up-conversion) and IFFT/FFT and CPaddition/removal. VRU will host all other parts of the stack as the CU.

Considering IFFT/FFT and CP addition/removal, the only parts of overallprotocol stack which are not load dependent and they are in DU for split7.1, this split can be utilized for extreme load balancing scenarios.For morphologies and geographical areas with very non-uniform peakloads, this split can exhibit maximum sharing gain. This is shown inFIGS. 16A and 16B.

DL

For a 20 MHz channel, 256QAM and 8 layers the required bitrate is:

100 (PRB)×12 (no of subcarriers per PRB)×14 (symbols)×8 (bits persymbol)×8 (layers)×2 (I/Q)/1×10-3

(one subframe)=2.15 Gbps

UL

For a 20 MHz channel, 64QAM and 8 layers the required bitrate is:

100 (PRB)×12 (no of subcarriers per PRB)×14 (symbols)×6 (bits persymbol)×8 (layers)×2 (I/Q)/1×10−3 (one subframe)=1.61 Gbps

For split 7.1 the fronthaul needs to support 3.76 Gbps bidirectional

The one-way latency of 250 microseconds is expected for split 7.1option.

Parallel Wireless complies fully with 3GPP standards. Therefore, anyvendor with standard IFFT/FFT and CP addition/removal (Low-PHY) can beconnected to the Parallel Wireless CU (HNG).

Low latency and high throughput requirements for split 7.1 may be anissue for connecting DUs to CU. However, this split is one of the bestoptions to take advantage of sharing gain and utilize different peakload rates across the network.

As it described in our previous responses, a majority of theload-related processing in this split is collocated with CU (VRU), whileless load-dependent processing (FFT/IFFT) is collocated with DU (CWS).

Our CU portion of the split 7.1 solution leverages both GPP and FPGAs.We employ RTOS (real-time operating system) at the CU to orchestrate theHW resources running on the FPGA for Low-PHY processing. Therefore,there will be enough processing power to support this split in our DU.The same RTOS is also powering our scheduler, High-PHY, MAC, RLC, PDCP,RRC and RRM functionality in the higher layers of the protocol stack.Our GPPs are commodity server chips based on x86 architecture and the SWruns on real-time Linux.

For deployment in dense urban areas, Parallel Wireless recommends split6, in order to keep RF and PHY at CWSs and using less than perfectfronthauls to connect them to VRU which hosts PDCP, RLC, and MAC as thecentralized unit. Both CWS and VRU support this split and can beutilized for deployment.

Legacy centralized baseband (split 8) in most cases promises loadbalancing between sites, taking advantage of the fact that peak loads donot occur uniformly. However this must be balanced against any increasein the cost required to achieve the load balancing, e.g., for switchingradio traffic between different processors. Field studies have foundthat a relatively small number of base stations still provide goodheterogeneity, and that most of the potential for load balancing gainscan be leveraged with about 20 sites. In addition, certain“computationally expensive” processing tasks such as fast Fouriertransform/inverse fast Fourier transform (FFT/IFFT) are not loaddependent and exhibit no sharing gains. Also, considering HARQmanagement at the MAC level is one of the most traffic related processesit will be beneficiary to utilize split 6 for scenarios where there aresites with different demographics (e.g., business and residential) andless than perfect backhauls in terms of latency (around 8 msec RTT).This is shown in FIGS. 17A and 17B.

Based on 3GPP TS 36.213 for DL, 8 layers, 256QAM, the TB bits are 391656(per TTI) therefore the maximum DL through put will be 391 Mbps. Foruplink, assuming category 17/19 (supporting 256QAM) the UL TB bits are211936 (per TTI) therefore the maximum UL through put will be 212 Mbps.

Considering the 30% overhead, the maximum bi-directional link capacityfor split 6 will be: (391+212)*1.3=784 Mbps

Considering the 8 msec RTT requirements, standard 1G WAN connectionswould be sufficient for split 6 fronthaul.

For calculating the required RTT for this split, we must look into HARQtiming for PRACH and regular data transmission. For the PRACH, eNB isrequired to answer to the UE within a configurable random-accessresponse window. This window starts three subframes after the lastsubframe with the respective preamble transmission and has aconfigurable length between two to ten subframes. Considering theshortest duration for two subframes (2 msec), the UE must receive itsresponse before 4 msec. Considering maximum ranges for LTE (100 Km) andits related timing advance (0.67 msec) and about 1.5 msec for processingtime at the CU, it left us with 2 msec RTT for latency between MAC andPHY. Therefore, a maximum one-way latency of 1 msec is required for thissplit.

The standard synchronous transmission and ACK messages which have 8 msec(8 subframe after the initial one) delay budget will not be a dominantfactor for this requirement.

Parallel Wireless complies fully with 3GPP standards. Therefore, anyvendor with standard PHY interface (and standard RF) can be connected toParallel Wireless CU (HNG).

Because FFT/IFFT are very “computationally expensive” processing tasksand not load dependent (they don't provide any sharing gain), ParallelWireless believes combining PHY and RF units (split 6) is one of themost efficient splits.

As it described in previous questions, majority of the load relatedprocessing in this split is collocated with CU (HNG), while less loaddependent processing (including FFT/IFFT) is collocated with DU (CWS).

Parallel Wireless supports multiple split options with a goal ofproviding greater flexibility in system deployment while at the sametime improving latency and reliability. The Split 6 solution requiresthat the radio is collocated with PHY, whereas the CU contains MAC, RLC,RRC and PDCP. Our CU functionality is aggregated across multiplesectors/sites and is realized through a GPP solution. Our GPP componentsinclude, but are not limited to, multi-core processors with real-timeoperating system and optional FPGA-like processing modules to offloadcompute-intensive operations such as PDCP ciphering, RRC AS SRBintegrity protection and SRB/DRB ciphering, and deep packet inspectionas part of our application intelligence. Also, all layer 2functionalities, including HARQ scheduling is located at CU. This willutilize load balancing and take advantage of the fact that peak loadsnot occurs uniformly across sites.

Parallel Wireless's DU solution for Split 6 also involves GPP along withFPGAs to accelerate the layer 1 (PHY) processing. Some of the basebandfunctionality such as channel estimation, equalization, MIMOprecoding/decoding, and time/frequency-domain scheduling are implementedin the GPP whereas the processing intensive operations such as Turbodecoding are implemented in the FPGAs.

Option 2 split is recommended for deployment in dense urban areas withnon-ideal backhaul. In the Parallel Wireless Solution Option 2 splitcould be realized with RRC, S1-U (data) and PDCP functions to beco-hosted with the VRU and the Lower layers RLC, MAC and PHY on the CWS.This option allows some part of the stack to be virtualized. The PDCPRLC split is already standardized in the LTE dual connectivity.

This option would be ideal in case the backhaul is unable to ensurelatency/jitter requirements of some of the lower split options and inimplementation would mean a very straight and clean split. The overheadof traffic is also minimal and is comparative to non-split fronthaulrequirements. Option 2 split enables virtualization of some part of thestack function and also provides the option to reduce processingoverheads on the RRH or DU. Another advantage of this split option,especially with Parallel wireless solution, is the Dual Connectivitywill be very efficiently implemented and back routing of data packetsover the X2 interface is avoided. Since the VRU/HNG is close to EPCthere is significant overhead reduction in packet routing when Option 2split is implemented with the VRU/HNG. This is shown in FIGS. 18A and18B.

This option could be further enhanced to separate the RRC to the CPstack and PDCP to the UP stack which enables scaling of the user planeload.

Based on 3GPP TS 36.213 for DL, 8 layers, 256QAM, the TB bits are 391656(per TTI) therefore the maximum DL through put will be 391 Mbp. Foruplink, assuming category 17/19 (supporting 256QAM) the UL TB bits are211936 (per TTI) therefore the maximum UL through put will be 212 Mbps.

Considering the 5% overhead, the maximum bi-directional link capacityfor split 2 will be: (391+212)*1.05=637 Mbps

This Option latency requirement is similar to non-split versions andminimum latency could be based on the application and control planelatency requirements. For instance, if Control plane latency needed tohave Idle to Connected mode transition in 100 msec and the access sideprocedures need 60 msec for the air interface messages, minimum latencyrequired could be de-rived based on Number of Control Messages exchangedbetween RRC and MAC/PHY and RTT for each message so that this doesn'texceed 10 msec duration.

Parallel Wireless complies fully with 3GPP standards. Therefore, anyvendor with standard RLC interface can be connected to the ParallelWireless CU (HNG).

Considering the fact that HARQ is directly related to the cell usertraffic, this split will provide a very high sharing gain. If the peaktimes do not occur uniformly across the network, this split can be oneof the best candidates.

HARQ and other parts of the stack above the MAC layer will be the majorconsumer of baseband processing in this scenario.

Parallel Wireless supports multiple split options with a goal ofproviding a greater flexibility in system deployment while at the sametime improving the latency and reliability. The Split 2 solutionrequires that the radio is collocated with the PHY, MAC and RLC (i.e.,the DU functionality) whereas the CU contains RRC and PDCP. Our CUfunctionality is aggregated across multiple sectors/sites and isrealized through a GPP solution. Our GPP components include, but notlimited to, multi-core processors with real-time operating system andoptional FPGA-like processing modules to offload compute-intensiveoperations such as PDCP ciphering, RRC AS SRB integrity protection andSRB/DRB ciphering, and deep packet inspection as part of our applicationintelligence. We also note that Parallel Wireless DU solution for Split2 also involves GPP along with FPGAs to accelerate the layer 1 (PHY) andlayer 2 (MAC/RLC/Scheduler) processing. Some of the basebandfunctionality such as channel estimation, equalization, MIMOprecoding/decoding, and time/frequency-domain scheduling are implementedin the GPP whereas the processing intensive operations such as Turbodecoding are implemented in the FPGAs.

As we described in the general section, Parallel Wireless supports allsplit options with a goal of providing a greater flexibility in systemdeployment while at the same time improving the latency and reliability.Any split can be supported by utilizing the dynamic Parallel Wirelesssolution based on specific morphology and fronthaul limitation.

Any one-way latency from +40 msec (split 1) all the way to 250 microsecond (split 8) can be supported by Parallel Wireless solution.

As described above, RAN virtualization (abstracting the underlying basestations from the core network using the HNG between the RAN and core;see documents incorporated by reference) brings the flexibility todecouple the radio and RF from the base band processing and allocateresources; when and where needed, through the most optimized manner.Parallel Wireless solution provides all necessary requirements toaddress this requirement based on its HNG by providing abstraction, corenetwork isolation and resource utilization.

In general, for rural and remote areas with lower number of users, lowertraffic and less than perfect fronthauls, access schema split 0 is thepreferred one. At the moment, Parallel Wireless 3G/4G solution deployedacross the world with HNG as the aggregator located remotely in operatorcolocation facilities and CWSs acting as a compact RRU/DU/CU single unitwith different fronthauls including commercial LTE services and DSLs.

On the other extreme in super dense areas; e.g. stadium, shopping malls,DU/CU/Aggregator are going to located in the vicinity, a low latency andreliable fronthaul (CPRI type of connections) can connect all RRUs tothe central local location through a high throughput low latencyfronthaul.

Parallel Wireless believes Massive MIMO technology is a promisingtechnology in order to address future 5G requirements for higherspectral efficiency and utilizing mmWave for access networks.Full-Dimension MIMO (FD-MIMO) targets the systems utilizing up to 64antenna ports at the transmitter side has been already defines in 3GPP.

In general, as the number of eNB antennas increases, cross-correlationof two random channel realization goes to zero and therefore theinter-user interference in the downlink can be controlled via a simplelinear precoder and reduced complexity and cost. However, this canachieve when perfect channel state information (CSI) is available ateNB. Accurate CSI acquisition in TDD system is relatively easy, but isnot the case for FDD systems where time variation and frequency responseof channel the channel are measures via the downlink reference signalsand send back to the eNB after quantization. Even in TDD mode, thesystem cannot solely rely on the channel reciprocity because themeasurement at the transmitter does not capture downlink interferencefrom neighboring cells. Therefore, downlink reference signals arerequired to capture CQI for TDD.

We believe these two major problems related to CSI acquisition;degradation of CSI accuracy and increase in pilot overhead, need to beaddressed before we witness major massive MIMO deployments. ParallelWireless is already working to address these issues.

Parallel Wireless's SON functions are located at our HNG, and thereforewill be an integrated part of our vRAN solution. It is amulti-technology platform facilitate all three elements of SON;self-configuration, self-organization and self-optimization. Allfundamental functionalities; including but not limited to, mobilitymanagement, interference management and load management will be handledthrough SON across technologies. Because of Parallel Wireless's HNGlocation (sitting between core and RAN) and functionalities, it canprovide the most efficient SON compare to other available solutions.

As we have described in previous sections, based on type of splits andnetwork requirements, our CWS radio functionalities can be changeddynamically. It will depend on the type of services offered, morphologyand fronthaul limitations.

The Parallel Wireless HNG can be deployed as a VNF (it is a CompositeVNF, which includes a federation of VMs behaving like a single logicalentity). HNG is ETSI's MANO compliant, and agnostic to the underlyingData Center infrastructure (i.e.: Intel x86 commercial off the shelfservers) and can be installed on top of all major market leadinghypervisors (Linux KVM, VMware ESXi). Furthermore, HNG can be managedvia any standards-compliant VNF Manager (VNFM), as well as any NFVOrchestrator (NFVO).

Taking into consideration operator needs to introduce 5G services intoexisting 4G network, and in line with industry trends for 5G adoption,Parallel Wireless solution is planning to support NSA Options 3/3a/3x,as well as Option 7/7x and Option 2. Parallel Wireless unique approachwith its HNG enables operators to significantly simplify existing2G/3G/4G networks and ease its evolution towards 5G.

The new RAN introduced by 5G states a coexistence of LTE eNodeB (eNB)and the newly added gNodeB (gNB). There are new interfaces defined inthis architecture:

gNB are interconnected with each other via the Xn interface

gNB are connected to the NGC via NG interface (Control Plane and UserPlane separately). This is shown in FIG. 19.

Those mobile operators launching 5G services with NR have severaldeployment options to support LTE and NG coexistence and evolutiontowards a pure-5G network, as shown below:

Option 3/3a/3x: Uses LTE Mobile Core (EPC) only with LTE eNB and 5G gNB.The LTE eNB is connected to the EPC in Non-standalone NR (NSA). NR'sUser Plane to EPC goes via the LTE eNB (option 3) or directly (option3a). This can be the first deployment phase, where 5G NR RAN as well as4G RAN use existing 4G/LTE Mobile Core. In this case, EPC shall supportDual Connectivity.

Option 7/7a/7x: Once the Mobile Core is upgrade to Next Gen Core (NGC),the LTE eNB is connected to it with NSA NR. The UE User Plane canconnect to the NGC via either eNB (option 7) or directly (option 7a).

Option 2: this would be the case of a greenfield 5G scenario, involvingonly NGC and gNB (no 4G LTE or eNB RAN).

Although 3GPP has specified a few other options, it is accepted in theindustry that the above cases will be the most likely to be deployed forpractical reasons.

In principle, the Xx interface implemented by the Parallel Wirelesssolution is going to be based in 3GPP guidance, although the finalspecification will become available as part of Release 15 TechnicalSpecifications. This is shown in FIG. 20

Parallel Wireless supports a standard Xn 3GPP-based interface to thirdparty eNBs.

Parallel Wireless's advanced filtering solution has been tested tosupport B3+n78 dual connectivity.

Parallel Wireless is investigating the various techniques that canreduce out of band (OOB) spectral emissions in 5G.

At present PW are considering W-OFDM (weighted orthogonal frequencydivision multiplexing) as a compromise between complexity andperformance.

Other techniques are also under study such as UFMC (universal filteredmulticarrier), FBMC (filter bank multicarrier) and F-OFDM (filteredorthogonal frequency division multiplexing). Higher performance may bepossible with these techniques, for instance with FBMC, but complexityof implementation requires further study.

Mini-slots may be supported in the future, for equipment operating above6 GHz.

At present Parallel Wireless's main portfolio operates within or belowthe 3.5 GHz bands

Existing equipment does not support the bands allocated for SupplementalUL e.g. L-Band, but PW can develop support if the size of theopportunity/award to PW is sufficiently large.

For shared spectrum, PW already supports products many appropriate bandse.g. 700, 800, 900, 1800 and 2100 MHz and shall extend support using 5GNR.

We consider a combined RRU/DU as the most efficient way for deployingthe future generation wireless network. Since lower layer PHY (includingIFFT/FFT) functions are not load related and require very highthroughput and delay sensitive fronthaul if separated from RRU, it willbe feasible to consider split 6, with an RRU/DU unit and a combinedaggregator/CU in colocations. In case of challenges to provide reliablefronthaul for this scenario (as is discussed in detail in Split 6section), split 2 can be the second-best option.

Splits 2 and 6 are the most suitable economic solutions based on acombined RRU/DU and combined aggregator/CU. For scenarios wherepopulation density is low and high throughput/low latency fronthauls areexpensive, split 2 will provide service to the subscribers in aneconomic and technically desirable way. In more dense scenarios withmore available options for fronthaul, split 6 will be the best scenariofor deployment.

A new solution using Option 6 (MAC-PHY split) is described below. Theconceptual solution is to move L2, L3 to BBU, while leaving L1, Rf/Uu atthe CWS. This can be done with well-known hardware, for example usingDPDK fastpath at the RAN node and the VRU. Central to the implementationis a special VRU (virtual BBU or virtual radio unit). The VRU can use anadvanced femto API to communicate with the Parallel Wireless CWS. ThisVRU does not connect to the core network but instead connects to theParallel Wireless HNG. It is multi-RAT-aware and -capable (2G, 3G, 4G).Virtual machines and/or containers are managed by a host hypervisor,which enables resource allocation among multiple CWSes. The HNG can beused for management, using S1 via TR69. SON may be offloaded to BBU,pool of resources for a BBU, e.g., PCI.

This new solution may be capable of flexible splits. The splits can behybrid or heterogeneous splits, which are new. Suppose CWS A is heavilyloaded. Processing can be moved to the VRU, e.g., for a single CU(central unit), DU (distribution unit) A (with option 3), or DU B (withoption 6), i.e., two different splits off of the same CU. The newsolution can have the ability to dynamically transition these splits,to/from the CU or between/among DUs. The new solution can dynamicallysupport either Split 6 or Split 7, in some embodiments.

For rural deployments, for example, a fixed split is often not ideal.Rather, a flexible split is appropriate. The ability to push only PHY,or also push MAC, or adjust the split, is very helpful, particularlywhen the split can be based on current backhaul or fronthaul conditions.The FFT portion does not need to be performed at the BBU (VRU) either,because as the FFT portion is load-invariant. A dynamic way to push MACfrom some CWS to dedicated VRU is therefore very helpful.

The ability to change the split and distribute functionalities/networkelements based on capacity/latency of fronthaul is significant. This isdone by having HNG evaluate fronthaul capacity/latency and dynamicallyenable and utilize protocol stacks on CU and RU to match the fronthaulcapability. Our modular architecture and the fact that our GPP/FPGA HWat our CWS can provide enough horsepower to run protocol stacks at theedge. Further, this can be linked to SON—not only making changes inconfigurations, as with legacy SON, but changing protocol stacks asrequired.

Different types of containers may be enabled, e.g., 1 container type foreach split type. When we see that the CWS is loaded (either at the HNGor at the VRU), we can transition to a new container. L2, L3 RF istransient and therefore stateless; good for containers. We note that MACmay need to be moved across machines, and MAC is not stateless, e.g.,MAC may need to be moved to or from the CWS and the VRU. This problemcan be solved by moving UE context data. Moving MAC to/from CWS is newto this solution.

Use cases include: deployment of CWS to rural; add VRU to effectivelyutilize resources; deploy a big server, or even a small server, to thatlocation to selectively provide more powerful service as needed.

3GPP TR 38.801 is hereby incorporated by reference in its entirety. The3GPP TR 38.801 is referred to explain technical details of the presentdisclosure, as well as to explain the inherent possibilities andcapabilities of embodiments of the present disclosure. For example,shared RAN among multiple operators is also contemplated in conjunctionwith the discussion in 3GPP TR 38.801, e.g., § 5.5.

Noteworthy is that, while 5G New RAN is contemplated for 5G gNBs, thepresent disclosure is intended for use by operators to provide any andall combinations of 2G, 3G, 4G, and 5G, as well as Wi-Fi. For example,the various splits discussed herein could be used with one or more ofthese RATs or with some combination thereof, including hybrid splitswith different splits for different RATs. For example, an Option 6 splitmay be used for 4G, while an Option 7 split may be used for 5G, and nosplit may be used for 2G and 3G, with all of the 2G, 3G, 4G, and 5G basestations being able to be shared among multiple operators.

In the present disclosure, the word “dynamic” is meant in at least twosenses, and sometimes both, as appropriate given the context. In allsenses of the word, the word indicates that the hardware is equipped toprovide flexibility to the network operator. In one sense, flexibilityis provided at the deploy stage, i.e., before the equipment is deployedfor use. This is in accordance with the network owner's typical planningprocess for deploying a network. In another sense, the equipment may beable to be modified in its functional split after the deploy stage,i.e., after it has been deployed for use or even while it is inoperation. In some embodiments, changing a functional split may beenabled after a reboot. In some embodiments, changing a functional splitmay be enabled without reboot and on a per-user or per-UE or per-bearerbasis, i.e., the equipment may be enabled to change the split forindividual users when new bearers are created or even while a singlebearer is already in use. Different RATs may be treated differently withregards to splits, e.g., 3G may use an Option 4 split while 4G may usean Option 8 split.

In some embodiments, a CWS architecture may be used in which a radiohead is coupled with an offboard, upgradeable baseband module. A digitalfronthaul interface such as CPRI may be used between the modules. Theoffboard baseband module may be enabled to provide any of 2G, 3G, 4G,5G, Wi-Fi, or any other baseband; the digital fronthaul interface shouldbe designed with sufficient speed to support transmission of radiosamples prior to baseband processing. In some cases, the digitalfronthaul interface may be coupled with a baseband processor internal tothe radio head (i.e., onboard), and use of the offboard baseband andonboard baseband may be switched dynamically based on desiredperformance, power usage, available processing power, and other factorsas described herein. MIMO, multiple carriers, and other advancedfeatures that require more bandwidth will require provisioning ofgreater fronthaul bandwidth capacity. Fiber optic or Ethernet could beused as the physical fronthaul medium.

The various functional splits are described herein with language (Option2, Option 5, Option 6, Option 7, etc.) that is well-known to those inthe art. However, it is not well-known for these functional splits maybe dynamically configurable, as disclosed herein. Also, it is well-knownfor multiple radio heads to share a single baseband unit (baseband“hoteling”). However, it is not well-known for the radio heads to beable to use the offboard baseband units as optional and configurable andswitchable. Also, it is not well-known to permit the optional useoffboard baseband for different radio access technologies. Also, it isnot well-known to manage the use of offboard baseband using a networkconfiguration server that takes into account various types of load onthe system (e.g., the HNG). Also, it is not well-known to have an RFchain with configurable input/output routing that is not hard-coded orhard-wired and has sufficiently high speed and low latency for it to beconfigured to be able to use different functional splits at differenttimes. Also, the use of orchestration software for managing splitsacross multiple containers, hardware processors (CPU and FPGA) in thesame CU (or DU) is also not well-known.

In various embodiments, various factors could be considered in decidingwhich functional split to choose. For example, aggregate data usage,aggregate signaling usage, user count, per-user data or signaling usage,fronthaul usage for a given link, backhaul usage for a given link,fronthaul latency for a given link, baseband processing load for a givenRAT and node, general purpose processing for a given node, type of databeing carried, required quality of service, mix of RATs, mix of datatypes, factors pertaining to a single base station or a set or subset ofbase stations, etc., could all be considered alone or in combination todetermine what functional split is appropriate at a given time or in agiven network context.

In conclusion, the Parallel Wireless solution envisions a dynamicsolution based on available fronthauls and service requirements.

Although the methods above are described as separate embodiments, one ofskill in the art would understand that it would be possible anddesirable to combine several of the above methods into a singleembodiment, or to combine disparate methods into a single embodiment.For example, all of the above methods could be combined. In thescenarios where multiple embodiments are described, the methods could becombined in sequential order, in various orders as necessary.

Although the above systems and methods are described in reference tobase stations for the Long Term Evolution (LTE) standard and the 3GPP 5Gstandard, one of skill in the art would understand that these systemsand methods could be adapted for use with other, present, past, orfuture wireless standards or versions thereof. Where eNB is mentioned, a2G base station, 3G nB, 5G gNB, or any other base station could be used.The CWS is a multi-RAT base station; the CWS is in some embodimentscapable of Wi-Fi meshing. Fronthaul data could be carried over backhaullinks to the VRU in some cases.

Although the above systems and methods describe the coordination ofbaseband resources happening at the VRU, this may occur at the HNG andHNG functions such as SON may be performed at the VRU, or bothcapabilities may be combined in a single unit or logical module. Theabove ideas may be applied to any and all of 5G NR, standalone andnon-standalone, 4G only, 3G/4G, 2G/3G/4G, or any other multi-RATdeployment architecture.

Although the above systems and methods describe specific hardwareconfigurations, the hardware for, e.g., VRU and HNG could involve anycombination or permutation of well-known data center hardware runningspecialized software or generic software as described herein.Containerization, OS-level or other virtualization methods could be usedand various networking techniques and topologies could be used for thehardware and software running on the hardware.

The foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. In some embodiments, softwarethat, when executed, causes a device to perform the methods describedherein may be stored on a computer-readable medium such as a computermemory storage device, a hard disk, a flash drive, an optical disc, orthe like. As will be understood by those skilled in the art, the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. For example, wirelessnetwork topology can also apply to wired networks, optical networks, andthe like. The methods may apply to LTE-compatible networks, toUMTS-compatible networks, or to networks for additional protocols thatutilize radio frequency data transmission. Various components in thedevices described herein may be added, removed, or substituted withthose having the same or similar functionality. Various steps asdescribed in the figures and specification may be added or removed fromthe processes described herein, and the steps described may be performedin an alternative order, consistent with the spirit of the invention.Accordingly, the disclosure of the present invention is intended to beillustrative of, but not limiting of, the scope of the invention.

The invention claimed is:
 1. A method for providing Radio Access Network(RAN) dynamic functional splits, comprising: determining, by a user fora RAN, a first split of different functionalities between a Central Unit(CU) and a Distributed Unit (DU), the functionalities including a RadioResource Controller (RRC), a Packet Data Convergence Protocol (PDCP), aRadio Link Control (RLC); a Medium Access Control (MAC), a PhysicalLayer (PHY), and a Radio Frequency Unit (RF); and wherein a systemdynamically provides a second split of the functionalities at a latertime based on factors including user count, fronthaul capacity,fronthaul usage, required baseband processing capacity, and latency, andwherein the CU and DU functionalities are located at a Virtual RadioUnit (VRU) for the second split and wherein the VRU continuouslyevaluates the fronthaul capacity or latency and dynamically allocates,enables or utilizes protocol stacks on CU or DU to match the availablefronthaul capability at any time.
 2. The method of claim 1 wherein theRLC comprises a high RLC and a low RLC.
 3. The method of claim 1 whereinthe MAC comprises a low MAC and a high MAC.
 4. The method of claim 1wherein the PHY comprises a low PHY and a high PHY.
 5. The method ofclaim 1 wherein first split comprises the CU including the RRC; and theDU including the PDCP, RLC, MAC, PHY and RF.
 6. The method of claim 1wherein another split comprises the CU including the RRC and the PDCP;and the DU including the, RLC, MAC, PHY and RF.
 7. The method of claim 2wherein another split comprises the CU including the RRC, PDCP and highRLC; and the DU including the low RLC, MAC, PHY and RF.
 8. The method ofclaim 1 wherein the first split comprises the CU including the RRC, PDCPand RLC; and the DU including the MAC, PHY and RF.
 9. The method ofclaim 3 wherein the first split comprises the CU including the RRC,PDCP, RLC and high MAC; and the DU including the low MAC, PHY and RF.10. The method of claim 1 wherein the first split comprises the CUincluding the RRC, PDCP, RLC and MAC; and the DU including the PHY andRF.
 11. The method of claim 4 wherein the first split comprises the CUincluding the RRC, PDCP, RLC, MAC and high PHY; and the DU including thelow PHY and RF.
 12. The method of claim 1 wherein the first splitcomprises the CU including the RRC, PDCP, RLC, MAC and PHY; and the DUincluding the RF.
 13. A non-transitory computer-readable mediumcontaining instructions for providing Radio Access Network (RAN) dynamicfunctional splits which, when executed, cause a system to perform stepscomprising: determining, by a user for a RAN, a first split of differentfunctionalities between a central Unit (CU) and a Distributed Unit (DU),the functionalities including a Radio Resource Controller (RRC), aPacket Data Convergence Protocol (PDCP), a Radio Link Control (RLC); aMedium Access control (MAC), a Physical Layer (PHY), and a RadioFrequency Unit (RF); and wherein the system dynamically provides-asecond split of the functionalities at a later time and wherein the CUand DU functionalities are located at a Virtual Radio Unit (VRU) for thesecond split and wherein the VRU continuously evaluates the fronthaulcapacity or latency and dynamically allocates, enables or utilizesprotocol stacks on CU or DU to match the available fronthaul capabilityat any time.
 14. A system for providing Radio Access Network (RAN)dynamic functional splits, comprising: a converged wireless system(CWS); a HetNet Gateway (HNG) in communication with the CWS; wherein auser determines a first split of different functionalities between acentral Unit (CU) and a Distributed Unit (DU), the functionalitiesincluding a Radio Resource Controller (RRC), a Packet Data ConvergenceProtocol (PDCP), a Radio Link Control (RLC); a Medium Access control(MAC), a Physical Layer (PHY), and a Radio Frequency Unit (RF); andwherein the system dynamically provides a second split of thefunctionalities at a later time and wherein the CU and DUfunctionalities are located at a Virtual Radio Unit (VRU) for the secondsplit and wherein the VRU continuously evaluates the fronthaul capacityor latency and dynamically allocates, enables or utilizes protocolstacks on CU or DU to match the available fronthaul capability at anytime.